Device for float-conveying of webs of material

ABSTRACT

A device for acting upon and float-conveying webs of material, more particularly paper, using air or another fluid medium, inter alia, for drying the web, including a number of spaced-apart air ducts (9) on at least one side of the path of the web (B) and in the form of &#34;nozzle chambers&#34;, each chamber having at least one nozzle region extending over the width of the web path, air outlets (D) between the nozzle chambers (9), a guide element (16) extending as far as the nozzle chambers (9) disposed between each pair of nozzle chambers on at least a part of the web path, and a joint or connection (18) between the guide element and the nozzle chamber (9) set back (19) relative to the side of the nozzle chamber facing the web path (E), the guide element having a closed central region (16a) and outlet orifices (17) at the sides thereof and opening into an air outlet (3).

CROSS REFERENCE TO RELATED APPLICATION(S)

This United States application stems from PCT International ApplicationNo. PCT/DE88/00275 filed May 6, 1988.

BACKGROUN OF THE INVENTION

The invention relates to a device for acting upon and float-conveyingwebs of material, more particularly paper webs.

In known devices in which air is blown against a moving web in order todry it, "nozzle chambers" are present and air is discharged therefromtowards the web, normally through slot-shaped nozzles (e.g., see GermanPatent Reference No. DE-PS 31 30 450). The nozzle chambers are spacedapart in the direction of travel of the web, the intermediate spacesserving as air outlets. The process of conveying webs of materialthrough such devices is beset with numerous problems. More particularlythe web must be held in transit so as to avoid contact with the nozzlechambers or other parts of the device, since otherwise the web may bedamaged or its surface may be adversely affected.

BRIEF SUMMARY OF THE INVENTION

An object of the invention is to take account of the existingdifficulties and construct a device of the initially-mentioned kindwhich guide s the web in transit with particularly good efficiency andalso obtains the other desired effects, i.e. dries the web or thesurface thereof, in advantageous manner. The invention also aims at anadvantageous construction of the device in particular. Other associatedproblems addressed by the invention will be clear from the followingexplanation Of the disclosed solution.

According to the invention, a guide element extending as far as thenozzle chambers is disposed between each pair thereof on at least partof the web path, and has a closed central area and orifices at the sidethereof and opening into the air outlets; lateral areas are provided onthe nozzle boxes and project beyond the adjacent parts of the guideelements in the direction towards a longitudinal plane through the webpath, and the angle between the outsides of the lateral areas and thelongitudinal plane is not less than 90°.

In an aforementioned device, the moving web is guided with particularefficiency and is protected from damage, and also advantageous effectsare obtained. More particularly the web can be guided in corrugatedmanner, which is very advantageous in many cases.

The lateral areas on the nozzle chambers, which project beyond the guideelements in the direction of the plane in which the web moves, can be atan angle of up to 90° to the aforementioned plane. In a veryadvantageous embodiment the lateral areas are constructed so that theyextend backwards like an undercut. The lateral areas are advantageouslysubstantially planar, but a curved embodiment is not excluded.

Advantageously a well-defined edge is formed at the transition betweenthe lateral areas of the nozzle chamber and the end face thereof. Thisis particularly advantageous as regards flow conditions.

The guide elements between the nozzle chambers can have various forms.Advantageously the closed central area of each guide element is madeplanar.

The guide element can have inclined parts, more particularly in atransition region between the central part and edge regions.Advantageously at least some of the orifices are formed in the inclinedparts.

In a device of the previously-explained kind, the nozzle chambersthemselves can be constructed in various ways. Particularlyadvantageously, individual air outlets, each opposite a respective guidesurface for the air flow, are provided in the nozzle region of eachnozzle chamber in the wall parts adjacent the air duct on both sides ofa transverse plane in the longitudinal direction of the air duct andperpendicular to the plane in which the web moves.

The outlets can be mouthpieces, individual nozzles or the like. In avery advantageous embodiment the air outlets are holes in the wall partsof the air duct.

The nozzle chambers, including the guide elements between them, can beefficiently manufactured and operate satisfactorily even under varyingconditions. Even if wall parts are slightly displaced under unfavourableconditions, the amount of air remains constant, and the flow cOnditionsare also fully maintained in the desired manner.

A particularly advantageous embodiment is characterized in that two wallparts formed with outlets are disposed directly adjacent one another andeach wall part at least partly constitutes a guide surface for the airflows leaving the outlets in the other wall part. This construction cangive very advantageous conditions in numerous cases. More particularlyit can be used to produce air flows in accordance with the "coanda"effect.

BRIEF DESCRIPTION OF THE DRAWINGS

With regard to further disclosure of the detailed features andadvantages of the invention, express reference is made to the followingexplanation with reference to the accompanying drawings and wherein.

FIG. 1, is a schematic perspective view of a unit equipped with devicesaccording to the invention for treating a moving web of material;

FIG. 2 is an enlarged schematic cross-sectional view of a part of FIG. 1showing an embodiment of the device;

FIG. 3 is a top plan view of part of the device in FIG. 2, seen from thelongitudinal plane of the web path;

FIGS. 4 and 5 are enlarged schematic detail views show details on alarger scale;

FIG. 6 is a view similar to FIG. 2 showing another embodiment of thedevice in

FIG. 7 is a view similar to FIG. 3 of part of the device in FIG. 6;

FIG. 8 is a greatly enlarged perspective view of part of FIG. 1

FIG. 9 is a top diagram of a nozzle region;

FIG. 10 is a plan view of part of a nozzle region;

FIG. 11 is a cross-sectional view of another embodiment of a nozzleregion taken through a nozzle chamber; and

FIG. 12 another embodiment of a nozzle region.

DETAILED DESCRIPTION

FIG. 1 shows a plant used e.g. for drying a paper web B which moves in astraight line in the direction of arrow P and is guided between a topunit l and a bottom unit 2. The de vices for driving the web are notshown and can be constructed in known manner. Air supply ducts in theform of "nozzle chambers" 9 are spaced apart in the longitudinaldirection of the web in the bottom part of unit 1 and in the top part ofunit 2, leaving spaces 3 serving as air outlets between the nozzlechambers 9 and connected to the interior of unit 1, the rest of which isenclosed by walls 4. The same applies to the nozzle chambers 9 in thebottom unit 2.

In this embodiment, the nozzle chambers 9 in the top unit 1 are offsetby half a spacing from the nozzle chambers 9 in the bottom unit 2, sothat a nozzle region 0 in a top nozzle chamber 9 is opposite a spacebetween two bottom nozzle chambers 9, and vice versa. However, thestructure can vary according to requirements and individualcircumstances.

A guide element 16 extending up to the nozzle chambers 9 is providedbetween each pair thereof and is formed with orifices 17 opening intothe air outlet 3. Various embodiments of such guide elements will bedescribed in detail hereinafter.

Air at the desired temperature and pressure travels through an inlet 5in the direction of arrow F1 into a distribution casing 6 in unit 1 andthence to a branch casing 7, connected to each nozzle chamber 9 byorifices (not shown). Corresponding remarks apply to the bottom unit 2.The air flowing from nozzle regions D travels over web 8 and through theorifice s in guide elements 16 into the air outlets 3 and thence intothe aforementioned interior of unit 1, which it leaves through an outletB. Corresponding devices for supplying and discharging to and from unit1 can be constructed in known manner. Arrow F2 denotes the outflowingair. The bottom unit 2 is provided with means for air guidancecorresponding to unit 1. Alternatively the aforementioned features canbe provided on one side only.

FIGS. 2 and 3 show an embodiment of the device on a larger scale. Guideelements 16 are provided between each top and bottom nozzle chamber 9and have substantially the same length as nozzle chambers 9 and, likethem, extend transversely to the direction in which the web moves. Theiredges abut the side walls 9a of nozzle chambers 9 and are connectedthereto in suitable manner, depending on the material used.Advantageously the guide elements 16 and the nozzle chambers 9 are madeof sheet-metal. The joints or places of transition are denoted by 18.

Each guide element 16 has a closed central region 16a. At the side ofthe central region, orifices 17 open into the air outlets 3. Theorifices are advantageously disposed in mutually offset rows.Advantageously the central closed region 16a of guide element 16 isplanar, but it can also be slightly curved if required.

On each side the central region 16a is adjacent bent parts 16c which inthis embodiment are also formed with the orifices 17. The bent partsmerge into edge regions 16c which can extend parallel to the centralregion 16a and as far as the connections 18 to the side walls 9a ofnozzle chambers 9.

The side walls of chambers 9 have lateral areas 19 which project beyondthe guide elements 16 or beyond the connection to the edge parts 16c ofguide elements 16 and in the direction of a longitudinal plane E throughthe web path. This is shown particularly clearly in FIG. 4. In thisembodiment, the angle β between the longitudinal plane E and the outerside of the laterally projecting areas 19 is about 90°.

It may be particularly advantageous with regard to flow conditions ifthere is a well-defined edge 20 at the transition between the lateralareas 19 and an end face 13 of nozzle chamber 9.

The nozzle regions 0 on nozzle chambers 9 can be constructed in variousways. The advantageous embodiment shown in FIGS. 2 and 6 will bedescribed in detail hereinafter.

The air from the nozzle regions flows as shown by arrows in FIG. 2. Theair flows follow parts of the end surfaces of nozzle chambers 9 inaccordance with the coanda effect and travel as illustrated by arrowsalong guide elements 16 until the air is discharged through orifices 17into regions 3. In the process, web B is advantageously guided withoutinterruption and is caused to corrugate, as shown in FIG. 2.

FIGS. 5 to 7 show another very advantageous embodiment. Similar orcorresponding parts are given the same reference numbers as in FIGS. 2to 4. In this embodiment the front side areas 29 of nozzle chambers 9each extend backwards like an undercut. The angle β between anaforementioned area 20 and the longitudinal plane E is greater than 90°,i.e. obtuse. The guide elements 16 can be connected to the side walls 9aof nozzle chambers 9 at places 18. Alternately, as shown in FIG. 6 theycan be continued by bent areas 28 which are at the same angle as areas29 and can be adjacent thereto or permanently connected thereto insuitable manner. In that case the outer sides of areas 28 are equivalentto the outer sides of areas 19. As before, reference 20 denotes awell-defined edge.

FIGS. 8 to 10 show an advantageous embodiment of the nozzle region D,with some modifications.

A wall 10 forming part of the boundary of an air supply duct 9 is shapedso that wall regions at an acute angle to one another merge into arespective curved part 12 adjacent plane parts 13. Parts 12 and 13 canbe described as a guide surface L for an air flow.

Wall regions 10 have air outlets in the form of punched holes 14, theoutlets on one side being offset relative to the outlets on the otherside in the longitudinal direction of nozzle region D, i.e. transverseto the direction of the web, as shown more particularly in FIG. 10. Thefacing regions of walls 10 constitute baffle surfaces 11. Air flowingfrom holes 14 on one side strike the baffle surface 11 opposite, andvice versa. Subsequently the air flows along the curved region 12 andthe adjacent region 13. In FIG. 8 this is diagrammatically indicated byline S on one side.

In the embodiment shown, the baffle surfaces 11 are each inclined at thesame angle a relative to a transverse plane V perpendicular to thelongitudinal plane E through the direction of travel of web B, as shownin FIG. 9. Alternatively the two baffle surfaces can be given differentinclinations, depending on requirements. FIG. 9 illustrates this bymeans of a chain-dotted baffle surface 11', which is inclined at anangle b greater than that of the other baffle surface 11.

Advantageously the inclination is in the range from about 10° to 40°.Angles of about 15° are particularly advantageous.

In the embodiment shown in FIG. 8, all parts are im the form of acontinuous wall 10, which is suitably bent in the bottom apical region.Alternatively, as shown by chain-dotted lines, the baffle surfaces 11can be separate wall parts 1O', which come together at the ends and arejoined in sealing-tight manner by spot welding or another suitablemethod.

Advantageously a nozzle region of the aforementioned kind is disposedapproximately at the center of a nozzle chamber 9 as shown in FIG. 1. Inother embodiments, two such nozzle regions are spaced apart on eachnozzle chamber 9.

Another possibility is to provide only one baffle surface 11 in thenozzle region, and suitable outlets will then be disposed opposite it.For example, the wall part 10 constituting the baffle surface 11 to theright in FIG. 8 can be without outlets 14, which are provided only inthe wall part 10 to the left in FIG. 8. In that case no guide surface Lneed be provided on this side, but wall part 10 can e.g. have a bentcontinuation 15 constituting a normal boundary of a supply duct, asshown by chain-dotted lines in FIG. 8.

Irrespective of the details of the embodiment, the diameter d of theoutlets is advantageously about 3 to 7 mm. The distances e between theoutlets (FIG. 10) may more particularly be in the range from about 10 to30 mm.

Optionally also according to the invention, more than one row of outlets14 can be provided and/or the outlets 14 can also be verticallystaggered.

The height of each wall part constituting a baffle surface 11 (FIG. 9)is advantageously in the range from H=15 mm to H=30 mm, although thisshould not be regarded as limiting.

The radius R of the bent part 12 adJacent each baffle surface 11 isadvantageously in the range from about 5 to 25 mm. Other values,however, are possible depending on circumstances.

FIG. 11 shows an embodiment in which a closure member 21 is disposed atthe base of the nozzle region D. Member 21 extends over the entire widthof air duct 9 and, on its side facing the plane in which web B moves,has guide surfaces 22 which in this embodiment are roof-shaped. Airoutlets in the form of bores 14 are formed in curved wall parts 23 inthe immediate neighborhood of guide surfaces 22, which bound the closuremember 21. The air flowing from bores 14 travels along the associatedguide surface 22 and then strikes the curved wall area 23, where thecoanda effect is operative as in the embodiment in FIG. 8, so that theair flows along this wall area and along the adjacent planar wall area13 and in the process acts upon and float-conveys the web B.

Advantageously the closure member 21 is an exchangeable unit ready forfitting. More particularly it can e.g. be a drawn sectional metal part.

A closure member of the aforementioned or similar kind can simply beinserted between two wall parts 24 of air duct 9, the wall parts bearingtightly against the closure member. The closure member can be securede.g by screws 26, indicated by central lines only in FIG. 11, andextending through boles in flange parts 25 of air duct 9 and in flangeparts 27 of closure member 21.

FIG. 12 shows a closure member 31 which, like the closure member 21 inthe embodiment in FIG. 11, is disposed at the base of the nozzle regionD and has guide surfaces 32 on facing sides of a part 33 projecting inthe transverse plane V in the direction of the plane E in which the webmoves.

As before, air outlets 14 are provided in the immediate neighborhood ofthe beginning of the guide surfaces 32 in wall parts 23. Air flowing outof orifices 14 is guided by surfaces 32, so that the jet is deflectedsubstantially perpendicular to the plane of motion E.

As an alternative to the embodiment in FIG. 12, the projecting part 33of closure member 31 can lie outside the transverse plane V, moreparticularly at an angle thereto. Also, the two guide surfaces 32 canhave different positions or inclinations relative to one another. Thesame applies to the guide surfaces 22 in the embodiment in FIG. 11.

Some important features of the invention will be discussed in generalhereinafter, together with some special features.

The air outlets 17 in the nozzle regions or the associated wall partscan also be nozzles instead of holes. Preferably, nozzle outlets of theaforementioned kind are produced from the wall material by pressing orstamping, so as to obtain an air jet in the desired direction.

In principle, the air outlets 17 may advantageously be disposed in wallparts 10 or 23 so that the air flowing therefrom travels round thefacing bent surface of nozzle chamber 9 and, if no web is present, thentravels towards the orifices 17 in the guide elements 16.

More particularly, an embodiment of the aforementioned kind is presentalso in those end regions of the nozzle chambers D which normally lieoutside the area occupied by the web. This has an advantageous lateralclosure effect and also advantageously influences the stability of webmotion

In the embodiments in FIGS. 2, 3, and 6, 7 the orifices 17 opening intothe air outlets 3 are formed in inclined parts 16b of guide elements 16.In another very advantageous embodiment the orifices 17 are in the edgeparts 16c, i.e. near nozzle chambers 9. In that case the guide elements16 have a closed central region 16a. The transition to the edge partscan either be an inclined surface or alternatively the cross-section atthis place can be approximately arcuate or circular. As a finalalternative, the guide elements 16 can be completely plane.

The closed central region 16a is essential, since pressure builds uphere, so that the web is efficiently held and guided at this place alsoIn the advantageous embodiment shown e.g. in FIG. 2 or FIG. 6, a nozzleregion D of a nozzle chamber 9 is opposite the central region 16a ofeach guide element 16. At this place, therefore, there is a region at alower pressure than the region on the other side of the web. Inprinciple, the web is guided with great stability by the alternatingreduced-pressure and pressure zones in the longitudinal direction of theweb. The same applies in the transverse direction of the web, so thatthe web is efficiently kept in position during travel and cannot movesideways.

According to the invention also, the construction of the nozzle regionscan vary within a plant or treatment section, e.g. the nozzles can be asin FIG. 11 in one part of the treatment section and as in FIG. 12 inanother part thereof.

All the features mentioned in the preceding description or shown in thedrawing should be regarded, either alone or in combinations, as comingunder the invention as far as permitted by the known prior art.

I claim:
 1. A device for acting upon and float-conveying webs ofmaterial travelling in a web path using a fluid medium for drying theweb, comprising:a plurality of spaced-apart ducts for conducing thefluid medium on at least one side of the path of the web and in the formof nozzle chambers, each chamber comprising a side thereon facing theweb path, and at least one nozzle region extending over the width of theweb path transverse to the direction of travel of the web for directingthe fluid medium toward the web path; air outlets between said nozzlechambers; a guide element disposed between each adjacent pair of nozzlechambers and between an adjacent air outlet and the web path andextending in the direction transverse to the direction of travel of theweb substantially the same length as said nozzle chambers; joint meansbetween each guide element and the adjacent pair of nozzle chambers setback relative to said side of said nozzle chambers facing the web path;a closed central region on each guide element having a width extendingin the direction of travel of the web; and outlet orifices at the endsof the width of said central region, said outlet orifices being spacedin the direction of travel of the web and opening into the adjacent airoutlet.
 2. A device as claimed in claim 1 and further comprising:alateral area on each nozzle chamber adjacent each joint means projectingsubstantially in a plane from each joint means toward the web path at anangle of at least 90 degrees.
 3. A device as claimed in claim 2 whereinsaid lateral areas on each nozzle chamber extend toward each other inthe direction away from the web path.
 4. A device as claimed in claim 2wherein said lateral areas are substantially planar.
 5. A device asclaimed in claim 2 wherein a well-defined edge is provided at thetransition between each lateral area and said side of each nozzlechamber facing the web path.
 6. A device as claimed in claim 1, whereinsaid closed central area region of each guide element is substantiallyplanar.
 7. A device as claimed in claim 1 wherein each guide element hasregions thereon inclined relative to the web path and at least some ofsaid outlet orifices are formed in said inclined regions.
 8. A device asclaimed in claim 1 wherein said orifices comprise a plurality of rows oforifices.
 9. A device as claimed in claim wherein said nozzle regioncomprises wall parts, individual nozzle outlets in said wall parts forfluid medium, and respective guide surface means on said wall parts, sothat fluid medium from said nozzle outlets is directed substantiallytoward said guide surface means and substantially transversely to theweb path.
 10. A device as claimed in claim 9 wherein said nozzle outletscomprise holes in said wall parts.
 11. A device as claimed in claim 9wherein said wall parts comprise two wall parts formed with said nozzleoutlets, and disposed adjacent one another and each wall part at leastpartly constitutes said guide surface means for the flow of fluid mediumemitted from said nozzle outlets in the other wall part.
 12. A device asclaimed in claim 11 wherein said nozzle outlets in said one wall partare offset in at least one of the direction of the width of the web pathand a direction substantially perpendicular to the web path directionrelative to the nozzle outlets in said other wall part.
 13. A device asclaimed in claim 9 wherein said wall parts comprise curved portionsthereon and said nozzle outlets are formed in said curve portions.
 14. Adevice as claimed in claim 9 wherein said wall parts comprise two planarwall parts each extending at an acute angle to a plane extendingtransversely to the web path and each merging into curved wall areas.15. A device as claimed in claim 14 wherein said nozzle outlets areformed in said planar wall parts.
 16. A device as claimed in claim 14wherein said planar wall parts are disposed on opposite sides of and atthe same angle to said transverse plane.
 17. A device as claimed inclaim 9 wherein said planar wall parts are disposed at different anglesto said transverse plane.
 18. A device as claimed in claim 9 whereinsaid acute angle is in the range from about 10 degrees to about 40degrees.
 19. A device as claimed in 18 wherein said acute angle is inthe range from about 14 degrees to 16 degrees.
 20. A device as claimedin claim 19 wherein said wall parts are on each side of a planeextending substantially transversely to the web path and said guidesurface means are provided between said nozzle outlets in the respectivewall parts and face said wall parts for guiding the fluid medium fromsaid nozzle outlets to flow in at least one of the directionssubstantially transversely to the web path and substantially parallel tothe web path.
 21. A device as claimed in claim 9 wherein said nozzleregion further comprises at least one closure member extending in thedirection of the width of the web path of said nozzle chamber at thebase of the nozzle region remote from said web path.
 22. A device asclaimed in claim 21 wherein said guide surface means are formed on asurface of said closure member substantially facing the web path.
 23. Adevice as claimed in claim 21 wherein said closure member furthercomprises a projecting part projecting toward the web path, and saidguide surface means comprises guide surfaces on opposite sides of saidprojecting part of said closure member.
 24. A device as claimed in claim22 wherein said guide surface means comprises roof-shaped guidesurfaces.
 25. A device as claimed in claim 22 wherein said guide surfacemeans comprises a boundary surface on said closure member and saidnozzle outlets are provided immediately adjacent said boundary surface.